Which statement accurately differentiates ischemic ATN from nephrotoxic ATN?

• A. Ischemic ATN is caused by nephrotoxins; Nephrotoxic ATN due to hypoperfusion
• B. Ischemic ATN results from renal hypoperfusion; Nephrotoxic ATN results from toxins; Both show muddy brown casts
• C. Both rarely present with oliguria
• D. Ischemic ATN presents with glomerulonephritis features

Answer: (B)

The main idea here is that acute tubular necrosis has two common triggers: ischemia from reduced renal perfusion and nephrotoxic injury from toxins, but the downstream effect in the kidney tubules looks similar in both scenarios. The key differentiator is the cause: ischemic ATN arises from hypoperfusion, while nephrotoxic ATN results from exposure to nephrotoxins. In both forms, you often see muddy brown (granular) casts in the urine due to tubular epithelial cell debris from necrosis.

That’s why the statement that ischemic ATN results from renal hypoperfusion and nephrotoxic ATN results from toxins is the best answer—the cause is different, but the shared feature (muddy brown casts) fits both. The idea that ischemic ATN is caused by nephrotoxins is incorrect, because it swaps the etiologies. Also, ATN commonly presents with oliguria, not rarely, and glomerulonephritis features are not characteristic of ATN since it is a tubular, not glomerular, pathology.